Thanks for your response.
Essentially I didn't change any code from the official BMI270-Sensor-API on Github when using it, if you are referring to that. Still the issue of not beeing able to load the config into the BMI270 persists. I feel that loading the config is necessary to even use the BMI270 because otherwise I won't receive any data from the DATA_X registers. Having no problems receiving data from the BMI160. Either way, loading the config through the "official" way doesn't work and also not in my own way. So I don't understand what the problem with this sensor is. I have two BMI270 and for both sensors the config won't load. I don't think that both sensors would have some internal problems, but I really tried a lot since the last 2 weeks to get this thing up and running.
See it from your previous software code, you didn't use BMI270 sensor API to access BMI270.
Yes I did not use the BMI270 sensor API to access the BMI270 because as explained before using it without any modifications, multiple versions of the API it didn't work for me.
Either way I managed to get it working with my own code now.